Power generator assembly comprising a non-rotating part and an electric device included on a rotating part

ABSTRACT

A rotating part that includes at least one generator unit having at least one coil, at least one permanent magnet and two pole shoes having pole surfaces facing radially outward is provided, The non-rotating part has an arc-shaped saddle adaptor of ferromagnetic material arranged with a radial distance to the pole surfaces. The saddle adaptor is configured to close a magnetic circuit passing via the pole shoes through the coil in a rotational position where the saddle adaptor overlaps with the pole shoes of the generator unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a United States National Stage Application claiming the benefitof International Application Number PCT/EP2016/052513 filed on Feb. 5,2016, which claims the benefit of British Patent Application 1502097.7filed on Feb. 9, 2015, both of which are incorporated herein byreference in their entireties.

FIELD OF THE INVENTION

The invention relates to a power generator assembly including a rotatingpart (16 a) and a non-rotating part (16 b).

BACKGROUND OF THE INVENTION

Power generator assemblies including a rotating part and a non-rotatingpart are widely known. A stator as a non-rotating part is then usuallyconfigured such that it encompasses the rotor as a rotating partcompletely.

One type of generator assembly is a so-called variable reluctancegenerator wherein a magnetic circuit powered by a permanent magnet andpassing through a coil is periodically opened and closed. The AC voltageinduced in the coil as a result of the oscillating magnetic field may beused to generate energy or to drive other devices.

In some applications, the room for a stator encompassing the rotor maybe limited and be available only on one side. For example in trainbogies with saddle type suspension, it may be possible to arrangeadditional structures on or in a saddle adapter, whereas structuresarranged below the axle may be excluded for security reasons and extremeenvironmental conditions.

BRIEF SUMMARY OF THE INVENTION

The invention seeks to provide a versatile generator assembly suitablefor use in situations where an amount or a quality of available space indifferent radial directions of a rotating part is inhomogeneous.

The invention relates to a power generator assembly including a rotatingpart and a non-rotating part, in particular to a power generatorassembly for use in a train axlebox, wherein the rotating part isconfigured to be mounted on an end cap.

It is proposed that the rotating part includes at least one generatorunit. The generator unit is preferably of modular type and includes atleast one coil, at least one permanent magnet and two pole shoes havingpole surfaces facing radially outward. The non-rotating part includes anarc-shaped saddle adaptor of ferromagnetic material arranged with aradial gap to the pole surfaces. The saddle adaptor is configured toclose a magnetic circuit passing via the pole shoes through the coil inat least one first rotational position where the saddle adaptor overlapswith the pole shoes of the generator unit, wherein the magnetic circuitis at least partially opened if the saddle adaptor does not overlap ordoes not overlap completely with both of the pole shoes.

The configuration described above works based on a variable reluctancegenerator principle in that the oscillating magnetic field of themagnetic circuit being periodically opened and closed induces anoscillating voltage in the coil of each generator unit. This oscillatingvoltage can be used for driving electronic devices arranged on therotating part as desired without external power supply.

In the context of the invention, the expression arc-shaped means thatthe saddle adaptor does not extend over the entire circumference butonly over a certain fraction thereof, wherein that fraction differs fromboth 0° and 360° by at least the angular length of a generator unit.i.e. the distance between the middle points or the outer edges of thepole surfaces.

In particular, the circumferential lengths of a generator unit and ofthe saddle adaptor are such that at least one second rotational positionexists where the saddle adaptor does not overlap with the pole shoes ofa generator unit. In this configuration, the magnetic circuit should beat least partly open and the magnetic flux will be significantly lower.The magnetic flux therefore changes from minimum to maximum when therotating part rotates from the second rotational position to the firstrotational position and vice versa.

In a preferred embodiment, the power generator assembly has at leastfirst and second generator units. Additional units can be added toincrease the output power if required. Preferably, the generator unitsare substantially identical to each other and are arranged adjacent toeach other in circumferential direction.

There is consequently a risk of magnetic flux leakage between thegenerator units, which might adversely affect the magnitude of thedifference between the maximum and minimum magnetic flux through agenerator coil as the rotating part rotates from the second rotationalposition to the first rotational position and vice versa.

According to a further development, this problem is alleviated in thatthe direction of magnetization of adjacent generator units is oppositelyoriented. In other words, adjacent pole shoes of adjacent generatorunits have the same magnetic polarity.

In a further development, leakage of magnetic flux is further reduced inthat an additional permanent magnet is arranged between the adjacentpole shoes of at least the first and second generator units. Suitably,the direction of magnetization of the additional permanent magnet issuch that the magnetic flux is oriented in the same direction as that ofthe adjacent pole shoes. The additional permanent magnet will bereferred to as a guide magnet and has the effect of repelling straymagnetic flux, so as to guide the flux to the saddle adapter.

In a still further development, the power generating assembly comprisesat least one shunt magnet which has the effect of increasing the netflux difference between maximum and minimum when a generator unitrotates between the first and second rotational positions. The at leastone shunt magnet is arranged in proximity to at least one of thegenerator units and is configured to produce a magnetic field that isoppositely oriented from the magnetic field produced by the at least onegenerator unit. When the at least one generator unit is not underneaththe saddle adaptor, i.e. in the “open” first rotational position, theshunt magnet reduces the net magnetic flux of the at least one generatorunit. The magnetic flux may even become negative. When the generatorunit is underneath the saddle adaptor, i.e. in the “closed”, secondrotational position, the shunt magnet also reduces the net magneticflux. However, the reduction in flux is relatively less when the unit isin the closed position, meaning that a greater difference between themaximum and minimum flux is achieved. This improves the power output ofthe generator unit.

In a preferred embodiment of the invention, the rotating part isconfigured to be mounted on an end cap configured to hold a bearing of atrain axle and the saddle adaptor is configured to be mounted on a trainbogie side frame.

If necessary, the rotating part comprises at least one counterweightunit configured to compensate for imbalances created by the arrangementof at least two adjacent generator units.

The counterweight unit may itself comprise a generator unit having atleast one coil, at least one permanent magnet and two pole shoes havingpole surfaces facing radially outward. For example, the rotating part ofthe power generating assembly may comprise a first generator device,having one or more circumferentially adjacent generator units, andcomprise a second generator device, having one or more circumferentiallyadjacent generator units, whereby the second generator device isarranged at an angular interval from the first generator device, whichinterval is selected to rotationally balance the rotating part.

As will be understood, the mass of and location of further components ofthe rotating part are taken into account when determining the angularposition of the counterweight unit.

According to a still further development, it is proposed that the saddleadaptor includes a main body part and at least one additional piececonfigured to increase the surface area of the saddle adaptor and/ordecrease the air gap provided between the saddle adaptor and the poleshoes. In the case of a train axle box, the main body may be integratedin the saddle or saddle adapter of a saddle type train bogie suspension.

In one example, the at least one additional piece comprises a toothedradially inner surface, such that a varying radial gap is providedbetween the saddle adaptor and the pole shoes. This has the advantage ofincreasing flux change. In a further example, the radially inner surfaceof the saddle adapter is directly provided with such a toothed profile.

The invention further proposes that the rotating part includes powerharvesting electronics configured to accumulate AC power generated bythe oscillating magnetic field passing through the coils.

Further, it is proposed that the rotating part includes at least onecondition monitoring sensor and a wireless transmitter that operateusing power generated by the at least one generator unit. The conditionmonitoring sensor may be a temperature sensor, a vibration sensor orother type of sensor for monitoring an operating parameter of interest.

The invention further proposes that the rotating part comprises a signalmonitoring device for monitoring an output signal from at least onegenerator unit. Suitably, the generated voltage signal is monitored. Thesignal is necessarily cyclical in nature and may thus be used todetermine rotational speed of the rotating part and, in the case of atrain axle, the linear distance traveled.

Signal amplitude may also be monitored. The amplitude varies dependingon the radial gap between the pole shoes and the radially inner surfaceof the saddle adaptor and on a degree of axial overlap between the poleshoes and said surface.

In the case of a train axle comprising a first and a second powergenerator assembly according to the invention at a first end and asecond end of the axle respectively, the monitored voltage signal fromthe first assembly and the second assembly may advantageously becompared with each other. A signal comparator can be employed forcomparing a first output signal from the first assembly with a secondoutput signal from the second assembly, for detecting a sidewaysmovement of the bogie side frame. If, for example, both signals exhibita similar change in voltage, this may be used to detect a sidewaysmovement of a train bogie that comprises the axle.

A yet further aspect of the invention relates to a train bogie includinga power generator assembly according to the invention.

The above embodiments of the invention as well as the appended claimsand figures show multiple characterizing features of the invention inspecific combinations. The skilled person will easily be able toconsider further combinations or sub-combinations of these features inorder to adapt the invention as defined in the claims to his specificneeds.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a schematic view of an end part of a train axle equipped witha power generator assembly according to the invention;

FIGS. 2A and 2B are schematic illustrations of the principle ofoperation of the power generator assembly;

FIG. 3A is a schematic illustration of a power generator assemblycomprising two adjacent generator units with magnetic fields oriented inthe same direction;

FIG. 3B is a schematic illustration of a preferred embodiment of theinvention comprising adjacent generator units with oppositely orientedmagnetic fields;

FIG. 3C is a schematic illustration of a further embodiment of anassembly according to the invention; and

FIGS. 4A and 4B are schematic illustrations of a generator unit of astill further embodiment of the invention, shown in first and secondrotational positions respectively.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic view of an end part of a train axle, wherein outerrings 10 a, 10 b of a double row tapered roller bearing configured tomount the axle 12 in the saddle type adapter 26 of a train bogie arevisible.

An end cap 14 is fastened to an end face of the axle 12 by means ofthree bolts and preloads a split inner ring of the bearing in an axialdirection. A rotating part 16 a of a power generator assembly accordingto the invention is provided on an outer rim of the end cap 14. Theouter rim of the end cap 14 is substantially divided in two halves. Onesection 16 c houses the electronics and the other half includes multiplegenerator units 18 a-18 d. Four generator units 18 a-18 d are providedin the embodiment illustrated.

The power generator assembly includes the rotating part 16 a and anon-rotating part 16 b. The generator units 18 a-18 d are of modulartype and essentially identical in configuration. Each of the generatorunits 18 a-18 d includes one coil 20 arranged between two permanentmagnets 22 a, 22 b and first and second pole shoes having pole surfaces24 a, 24 b facing radially outward each. In the embodiment illustrated,the first and second pole shoes are formed by first and second permanentmagnets 22 a, 22 b which are arranged such that a first pole surface 24a has a first polarity and a second pole surface 24 b has an oppositepolarity. The pole shoes may also be formed by opposite poles of asingle magnet.

The non-rotating part 16 b includes an arc-shaped saddle adaptor 26 offerromagnetic material, in particular iron, arranged with a radial gapto the pole surfaces 24 a, 24 b.

The saddle adaptor is configured to close a magnetic circuit passing viathe pole shoes 22 a, 22 b through the coil in a rotational positionwhere the saddle adaptor 26 overlaps with the pole shoes 22 a, 22 b ofone of the generator units 18 a-18 d, wherein the magnetic circuit is atleast partially opened if the saddle adaptor 26 does not overlap or doesnot overlap completely with both of the pole shoes 22 a. 22 b.

When the axle is rotating, the saddle adaptor 26 periodically passes thegenerator unit 18 a such that the magnetic flux will be periodicallyvarying. The oscillating magnetic field of the magnetic circuit beingperiodically opened and closed induces an oscillating voltage in thecoil of the generator unit. This oscillating voltage can be then usedfor driving electronic devices arranged in the electronics section 16 cof the assembly as desired without external power supply.

The circumferential lengths of the first generator unit 18 a and of thesaddle adaptor 26 are such that at least one rotational position existswhere the saddle adaptor 26 does not overlap with the pole shoes 22 a,22 b of the first generator unit. Specifically, the circumferentiallength of the saddle adaptor 26 is a multiple of the circumferentiallength and the pitch of the generator units 18 a-18 d such that theseare closed in a first rotational position and open in a secondrotational position.

The principle of operation is illustrated in FIGS. 2A and 2B, whereinthe saddle adaptor 26 and a first generator unit 18 a are illustratedwithout curvature for the sake of simplicity. FIG. 2A illustrates thecase where the saddle adaptor 26 does not overlap with the pole shoes 22a, 22 b of the generator unit. Mainly, magnetic flux passes from theNorth pole to the South pole of each permanent magnet 22 a, 22 b, asshown by the dashed magnetic field lines at the second pole shoe 22 b.There may also be a weak magnetic flux passing between the two magnets22 a, 22 b and through the coil, as illustrated by the dashed lineextending between the pole surfaces 24 a, 24 b of the generator unit 18a.

In the presence of a ferromagnetic material, i.e. when the saddleadaptor 26 overlaps with the pole shoes 22 a, 22 b of the generator unit18 a, the majority of magnetic flux is guided through the saddle adapter26, as illustrated by the dashed lines in FIG. 2B, and a magneticcircuit is formed that causes a strong magnetic flux to pass through thecoil. The arrows 34 in FIG. 2B show the direction of the principlemagnetic circuit that is generated. The associated magnetic field willbe referred to as the generator field.

When two or more generators are arranged next to each other, there is arisk of flux leakage between adjacent units. Consider the situationdepicted in FIG. 3A, in which a first generator unit 18 a and a secondgenerator unit 18 b′ are schematically shown. Again, the pole shoes ofthe generator units are formed by permanent magnets. The second poleshoe 22 b of the first generator unit 18 a and the adjacent first poleshoe 22 a′ of the second generator unit have opposite magnetic polarity.The dashed magnetic field lines indicate the magnetic flux that isgenerated between the two units 18 a and 18 b′. This flux representsleakage and will be generated when the units are in an “open” firstrotational position and in a “closed” second rotational position.Consequently, the flux through the coil 20 of each generator unit willbe less and the change in flux will be less, leading to lower powergeneration.

In a preferred embodiment of the invention, wherein the power generatingassembly comprises at least first and second generator units, fluxleakage between adjacent units is reduced, as illustrated in FIG. 3B.Here, the second pole shoe 22 b of the first generator unit 18 a and theadjacent first pole shoe 22 a of the second generator unit 18 b have thesame magnetic polarity. Consequently, the creation of a magnetic circuitbetween adjacent units is avoided. Some magnetic flux is still generatedbetween the North and South poles of each permanent magnet, whichrepresents a flux leakage within each generator unit 18 a, 18 b.

In a further development of the invention, the power generating assemblycomprises a guide magnet arranged between adjacent pole shoes 22 b, 22 aof at least one set of adjacent generating units 18 a, 18 b. The effectof the guide magnet 28 is shown in FIG. 3C, where the first and secondunits 18 a, 18 b are shown in a situation where both are underneath thesaddle adapter 26. The guide magnet 28 is magnetized in the samedirection as the adjacent pole shoes of the first and second generatorunits. As a result, “stray” magnetic flux is guided through the saddleadaptor and through the coil 20 of each unit, to enhance the desiredmagnetic circuit and generator field of each generator. Preferably, aguide magnet 28 is arranged between each set of adjacent generatorunits, as shown in FIG. 1.

In a still further development of the invention, at least one generatorunit comprises a shunt magnet, which has the effect of enhancing thepower efficiency of the unit. This will be explained with reference toFIGS. 2A, 2B, 4A and 4B.

The power output of the generator unit 18 a is dependent of themagnitude of the change in magnetic flux when the unit rotates betweenthe first and second rotational positions. In the first rotationalposition, as depicted in FIG. 2A, a weak flux 41 passes between the poleshoes 22 a, 22 b and through the coil 20. A much stronger flux 42 passesbetween the pole shoes 22 a. 22 b and through the coil 20 in the secondrotational position, as depicted in FIG. 2B. This gives rise to a firstchange in flux ΔΦ1, whereby ΔΦ1=Φ2−Φ1.

In the embodiment depicted in FIGS. 4A and 4B, the generator unitcomprises first and second shunt magnets 30 a. 30 b arranged radiallyinward of the first and second pole shoes 22 a, 22 b respectively andradially outward of the end cap 14. Apart from the shunt magnets, theunit of FIGS. 4A and 4B is identical to that of FIGS. 2A and 2B. Theshunt magnets 30 a, 30 b and the end cap 14, which is made of aferromagnetic material, produce a magnetic circuit, whereby theassociated flux passing though the coil will be referred to as the shuntflux, and is represented by arrows 32 in FIG. 4A. The flux passingbetween the pole shoes 22 a, 22 b and through the coil 20, illustratedby the arrows 33, will be referred to as the generator flux. The shuntflux is oppositely oriented from the generator flux and, in the openfirst position, shown in FIG. 4A, is stronger than the generator flux.The net flux Φ3 is therefore relatively weaker and may even be negativecompared to the flux Φ1 of the configuration shown in FIG. 2A.

In the closed position shown in FIG. 4B, the generator flux indicated byarrows 34 is significantly stronger than in the open position. Theoppositely oriented shunt flux interacts with the generator flux suchthat a net flux 44 passes through the coil 20. The net flux Φ4 issmaller than the initial flux Φ2 generated in the FIG. 2B configuration;however, the reduction is relatively less compared with the reduction inthe open position. This is particularly the case when the initial fluxΦ2 would result in saturation. Consequently, the resulting change influx ΔΦ2, given by Φ4−Φ3, is larger than the change in flux ΔΦ1 for theconfiguration without shunt magnets, leading to improved power output.

Further embodiments of the invention include cases where the rotatingpart comprises at least one counterweight unit configured to compensatefor imbalances created by the arrangement of generator units 18 a-18 d.In addition, the saddle adaptor 26 may include a main body part 26 a andat least one additional piece 26 b configured to increase the surfacearea of the saddle adaptor 26 and/or decrease the air gap providedbetween the saddle adaptor 26 and the pole shoes 22 a, 22 b.

The electronics section 16 c of the rotating part 16 a includes powerharvesting electronics configured to accumulate AC power generated bythe oscillating magnetic field passing through the coils and at leastone condition monitoring sensor such as a temperature sensor, anacoustic emission sensor or a vibration sensor for measuring operatingparameters of the bearing and/or of the axle. Further, the electronicssection includes a wireless transmitter can operate using power obtainedby power generated by the generator units 18 a-18 d.

The invention claimed is:
 1. A power generator assembly comprising: asaddle adapter configured to be engaged by a train bogie side frame tosecure an axle thereto; a rotating part configured to rotate underneaththe saddle adapter, a non-rotating part located radially outside of therotating part, wherein one section of the rotating part includes atleast one generator unit having at least one coil, at least onepermanent magnet and two pole shoes having pole surfaces facing radiallyoutward and another section includes electronic devices, the saddleadapter being configured to overlap the two pole shoes of at least oneof the at least one generator unit, wherein the non-rotating partincludes an arc-shaped saddle adaptor of ferromagnetic material arrangedwith a radial distance to the pole surfaces, and wherein the saddleadaptor is configured to close a magnetic circuit passing via the poleshoes through the coil in a rotational position where the saddle adaptoroverlaps with the pole shoes of the generator unit.
 2. The powergenerator assembly according to claim 1, further comprisingcircumferential lengths of the generator unit and of the saddle adaptorare such that at least one rotational position exists where the saddleadaptor does not overlap with the pole shoes of the generator unit. 3.The power generator assembly according to claim 1, wherein the rotatingpart is configured to be mounted on an end cap configured to hold abearing of a train axle and the saddle adaptor is configured to bemounted on a rail way bogie side frame.
 4. The power generator assemblyaccording to claim 1, further comprising multiple generator units eachhaving at least one coil, at least one permanent magnet and two poleshoes.
 5. The power generator assembly according to claim 1, wherein therotating part provides at least one counterweight unit configured tocompensate for imbalances created by the at least one generator unit. 6.The power generator assembly according to claim 1, wherein a radiallyinner surface of the saddle adaptor, which faces the pole shoes, has atoothed profile such that varying radial gap exists between the polesurfaces and saddle adapter.
 7. The power generator assembly accordingto claim 1, further comprising: an axle having an end face, an endcap ispositioned on the end face.
 8. The power generator assembly according toclaim 1, wherein power is provided to the electronics by the at leastone generator unit.
 9. A railway bogie side frame comprising: a sideframe, and a power generator assembly configured to function inassociation with the side frame, the power generator assembly having arotating part, and a non-rotating part, wherein one section of therotating part includes at least one generator unit including having atleast one coil, at least one permanent magnet and two pole shoes havingpole surfaces facing radially outward and another section includeselectronic devices, wherein the non-rotating part includes a saddleadapter having an arc shape and formed of ferromagnetic materialarranged with a radial distance to the pole surfaces, the rotating partconfigured to rotate underneath the saddle adapter, and wherein thesaddle adapter is configured to overlap the two pole shoes of at leastone of the at least one generator unit, wherein the saddle adaptor isconfigured to close a magnetic circuit passing via the two pole shoesthrough the coil in a rotational position where the saddle adaptoroverlaps with the pole shoes of the generator unit.
 10. The railwaybogie side frame according to claim 9, further comprising: an axlehaving an end face, an endcap is positioned on the end face.
 11. Thepower generator assembly according to claim 9, wherein power is providedto the electronics by the at least one generator unit.
 12. A railwaybogie side frame, comprising: a side frame, a power generator assemblyconfigured to function in association with the side frame, the powergenerator assembly having a rotating part, and a non-rotating part,wherein one section of the rotating part includes at least one generatorunit including having at least one coil, at least one permanent magnetand two pole shoes having pole surfaces facing radially outward andanother section includes electronic devices, wherein the non-rotatingpart includes an arc-shaped saddle adaptor of ferromagnetic materialarranged with a radial distance to the pole surfaces, and wherein thesaddle adaptor is configured to close a magnetic circuit passing via thepole shoes through the coil in a rotational position where the saddleadaptor overlaps with the pole shoes of the generator unit, the rotatingpart configured to rotate underneath the saddle adapter, wherein thesaddle adapter is configured to overlap the two pole shoes of at leastone of the at least one generator unit, and an axle with a first end anda second end which are respectively provided with a first powergenerator assembly and a second power generator assembly.
 13. The powergenerator assembly according to claim 12, wherein power is provided tothe electronics by the at least one generator unit.